1. Field of the Invention
The present invention relates to a speaker, and more particularly, to a speaker for generating sound waves in a low frequency audio region using a sound generator including piezoelectric ceramics.
2. Description of the Related Art
A conventional speaker having a sound generator including piezoelectric ceramics has been disclosed in Japanese Unexamined Utility Model Publication No. 60-108098. This will be explained by referring to the drawings.

FIG. 6 shows a speaker 100 including a case 101. The case 101 includes a main body 102 and a lid 103. A piezoelectric resonator 104, which forms a sound generator, is provided at the connection between the main body 102 and the lid 103. Then, a sound hole 105 and a sound pressure adjusting tube 106 are provided with the lid 103, whereby the inner portion of the lid 103 becomes a resonant box 107. The sound pressure properties of the speaker 100 are adjusted and controlled by adjusting the length and diameter of the sound pressure adjusting tube 106.
However, an object of the conventional speaker was to make the sound pressure properties smooth, and consequently, it was difficult to obtain sufficient sound pressure having a wide band of frequencies, and particularly having a wide band of low frequencies. Furthermore, the main parts functioned especially poorly, and resulted in an increase of the overall size of the speaker.
In order to solve the above problems, preferred embodiments of the present invention provide a speaker which has a very small-size and generates excellent quality sound at an expanded low frequency audio region.
According to one preferred embodiment of the present invention, a speaker includes a main body, at least a bottom surface of the main body being open, a film provided on the bottom surface of the main body, a sound pipe extending from a top surface of the main body toward the inside of the main body, and a plate-like sound generator provided inside of the main body and arranged substantially parallel to the top surface and the bottom surface, the sound generator including piezoelectric ceramics.
Furthermore, the sound pipe is preferably bent or divided within the main body.
As a result, the speaker according to preferred embodiments of the present invention radiates low frequency sound waves having two resonant points, the two resonant points being low frequency sound waves radiated from a sound pipe and low frequency sound waves radiated through a film, and therefore, the low frequency range of the totality of radiated sound waves is significantly increased and expanded.
Furthermore, by bending the sound pipe or dividing the sound pipe within the main body, it is possible to obtain a sound pipe having sufficient length while reducing a height or vertical dimension of the speaker.
Other features and advantages of the present invention will become apparent from the following description of preferred embodiments of the present invention which refers to the accompanying drawings.